This invention relates generally to a liquid crystal display device, and more particularly to a guest-host type liquid crystal display device, and in particular, to a guest-host type liquid crystal display device including liquid crystal driving elements arranged in a matrix array.
Presently there is widespread demand for devices which can display a wide variety of information rapidly and in great detail. Under these circumstances, information processing devices designed for personal use are under active development. These devices includes devices such as, a pocket calculator, an electronic wristwatches including a calculator and a portable electronic translator. These information processing devices designed for personal use must be small and thin. Additionally, the device must have displays which are driven at low voltages as the power consumption of the device must be low. In view of this many display devices designed for personal use which display information must possess the same characteristics.
It is expected that information processing apparatus, such as a portable television receiver will soon be widely accepted in the market. Such portable television receivers will receive television signals and display the image on a display device. The display device included in a portable television receiver, as well must be able to be driven at low voltages so that there is low power consumption as in the other personal information processing apparatuses. Additionally, the devices must be small and thin as well as possess the ability to display efficiently both inside and outside the home.
There are various types of display devices which initially satisfy these requirements. For example, a thin type CRT (cathoderay tube), a plasma display and EL (electro luminescence) display, a LED (light emitting diode) display, an EC (electro-chromic) display and the liquid display are currently under consideration for use. Among these types of display devices, the liquid crystal display most sufficiently satisfies the design requirements noted above and is now widely accepted for use as a display device for the electronic calculator and for electronic wristwatches.
There are principally two methods for driving a liquid crystal display. The first is the static driving method and the second is a multiplex driving (time sharing driving) method. Both driving methods are under consideration and are now being developed for driving the liquid crystal display device to be utilized in a television receiver. The static driving method is more desirable in the case of a portable television receiver in that the liquid crystal display is driven at low voltage and has a low power consumption.
In the static driving method, liquid crystal driving elements are arranged in a matrix on one of the base plates which constitute the liquid crystal display cell. Each of the driving elements includes an electrode for driving the liquid crystal. This electrode and associated liquid crystal driving elements constitute one picture element of the display device. The picture elements are selectively driven by external signals for displaying the desired image. In this case, the voltage applied to each liquid crystal driving electrode is statically applied to the liquid crystal material. In such a liquid crystal display cell one of the base plates is often opaque, and thus the device operates in a reflection-type display mode.
An example of the structure and circuit diagram of a statically driven liquid crystal will be described in connection with FIGS. 1-3. A device driven in a multiplex mode is shown in U.S. Pat. No. 3,862,360. The device of this patent includes a liquid crystal display panel formed by sandwiching a thin layer of liquid crystal material between a glass plate which has a transparent electrode covering one surface and a back plate which has a matrix array of reflective electrodes formed thereon. Individual addressing and storage circuits for each cell are formed contiguous to the reflective electrodes.
Such display devices operating in the DSM mode have the advantage that it is possible to display black and white images without a polarizer. However, since the current flowing in the liquid crystal layer is large as compared with a liquid crystal display device operating in the FEM (field effect mode) utilizing a twisted nematic liquid crystal material, its power consumption and its dependence in viewing angle are also very large. Accordingly, it has been difficult to apply the DSM type of display device to the portable television receiver. Accordingly, it is desirable to provide a liquid crystal display device which overcomes the disadvantages of the conventional liquid crystal device of the static driving mode which has been used in a television receiver using DSM liquid crystal material.